1. Field of the Invention
In the applicant's U.S. patent application Ser. No. 513,418, filed July 14, 1983 as a continuation-in-part of the present application, there is described an invention relating to method and apparatus for the transfer of objects, closely packed within an enclosure, between the interior of the enclosure and selected positions on the top deck of the enclosure. More particularly, the invention of the related application is directed to method and apparatus for transferring containers for the storage of fish in the hold of a vessel between the hold and the deck through a hatchway in the deck, and to a containerized fish handling system comprising suitable nesting containers, the transferring apparatus, and support and guiding structures within the hold of the vessel. The present invention relates to a stackable container of a novel construction especially suited to the storage and mechanical handling of fish aboard a fishing vessel at sea, using a system such as that described and claimed in U.S. application Ser. No. 513,418.
2. Description of the Prior Art
Known methods of holding fish onboard trawlers and discharging them from the hold are subject to a number of disadvantages.
One such method comprises the storage of fish below deck in large pens. Such pens are typically assembled during fishing operations by the fitting of corrugated aluminum boards (pen boards and shelving boards) into vertical stanchions permanently installed in the hold. Fish are subsequently removed by breaking down the pen boards and shelving and directing the loose fish to a conveyor system, air unloader or other impelling device to remove them from the hold. Storage of fish in pens utilizes space in the hold efficiently, but results in a deterioration of quality in the fish, arising in part from the considerable weight exerted on fish near the bottom of the pen by those above, and in part from physical damage that occurs during discharging.
Another method, which leads to the delivery to port of fish of a very high quality, employs the boxing of fish and ice in relatively small boxes (approximately 100 lb. capacity) and storage of such boxes by stacking them within the hold. However, boxing entails a high labour cost and the boxes employed and the manual procedures employed in their handling are volumetrically inefficient. Furthermore, neither boxing nor holding in pens lends itself to high rates of unloading fish from the hold.
Apparatus for handling fish containers to be stowed within the hold of a ship is disclosed in U.S. Pat. No. 2,448,373 (Hurst), which describes the gravity-controlled swinging of containers lowered into the hatchway towards either side of the hold by means of a system of ropes and pulleys. However, this system is not adapted to the rapid and volumetrically efficient storage and removal of the large number of relatively small, rigid containers required to ensure delivery of high quality fish to shore.
In accordance with the present invention which is the subject of continuation-in-part application Ser. No. 513,418, and which is described below to indicate the use of the stackable container of the present invention, there is provided a system of containerized fish handling which overcomes the deficiencies of prior systems of handling fish on board an ocean going vessel. This system allows the storage of fish in containers of sufficiently small interior depth to ensure delivery to port of a high quality product, while at the same time achieving high volumetric efficiency of fish storage within a hold compartment of a fishing vessel and high rates of discharge of containers from or transfer to a hold compartment.
According to applicant's containerized fish handling system, fish are stored in each hold compartment of the vessel in closely stacking, vertically mating containers. Each container is provided with extended side walls between which nests the container arranged immediately above it. The side walls of each container are provided with apertures or other suitable gripping sites adapted to be engaged from above by gripping means positioned over the container and between the extended side walls, thereby allowing containers to be removed from the hold compartment and yet be stacked close together therein, so that the maximum storage capacity of the hold compartment for containers may be utilized.
The rapid and efficient transfer of containers between storage positions in the hold compartment and working positions above the deck overlying the hold of the vessel is achieved by the use of an in-hold travelling hoist to move a plurality of containers to and from selected positions within the hold compartment in co-operation with an above-deck conveying system, including an above-deck hoist, operable to convey the plurality of containers between a position interior of the hold compartment directly below an open hatchway in the deck and a selected working position on the deck. Each hoist is provided with a vertically movable lifting frame having extendible projections adapted for engagement with or release from the gripping sites of a plurality of containers arranged end-to-end in a horizontal row, so that a row of containers may be thereby lifted from the next underlying row without disturbing the containers stacked in rows adjacent to the sides or bottom of the row being lifted.
Transporter assemblies which utilize the principle of horizontal movement of a lifting device on a track and of hoisting and lowering therefrom for the purpose of lifting cargo from within a hold of a ship to dockside and vice versa are known in the art of materials handling, as in U.S. Pat. No. 2,591,140 (Dougherty), U.S. Pat. No. 3,543,952 (Young), U.S. Pat. No. 3,630,390 (Tax), U.S. Pat. No. 3,881,608 (Hupkes) and U.S. Pat. No. 3,946,881 (Ludvigsen). Travelling crane assemblies which further provide for fore-and-aft motion of the entire lifting unit are also known for use with container ships, as in U.S. Pat. No. 2,456,104 (Andersen), U.S. Pat. No. 2,984,367 (McIntyre) and U.S. Pat. No. 4,049,132 (Stromback).
The apparatus described in U.S. patent application Ser. No. 513,418 differs from the prior art relating to marine transporter assemblies in disclosing a travelling hoist which operates beneath a deck of a fishing trawler at sea in co-operation with above-deck conveying apparatus in an efficient system for the transfer of containers suitable for the storage of fish between a working deck and selected locations in the hold.
Stackable, vertically interlocking packing or transport cases for the storage or transportation of fish in an ice-packed condition, which provide for outside drainage of melt water to prevent contamination of the contents of the lower container in a stack, are known. Examples of such containers are disclosed in U.S. Pat. No. 3,338,468 (Wilson), U.S. Pat. No. 3,366,273 (Crocella et al.) and U.S. Pat. No. 3,447,716 (Nesse). Cases of this type are not, however, provided with extended, slotted side walls to impart transverse strength to a stack of nesting containers while allowing for grasping and lifting of a container by a mechanism operating between the side walls. Interior gripping ability allows an array of such containers to be lifted without disturbing adjacent containers. In stackable containers according to the invention, the mating fit between the pair of extended, slotted side walls of one such container and the bottom longitudinal recesses of a container stacked immediately thereabove, the recesses being formed by the bottom of each container having a reduced width, a relatively large percentage of the volume occupied by the extended side walls of the container is recaptured in a stack of such containers to afford a higher volumetric efficiency than has been achieved with known nesting containers. The arrangement of mating elements in the stackable container according to the present invention permits the close packing of large, insulated (i.e. thick-walled) containers designed for mechanical handling, while at the same minimizing the effective loss of each container's storage capacity. A disadvantage of known containers, particularly of the relatively smaller fish boxes intended for manual handling, a decreased volumetric efficiency resulting from the space occupied in a stack of such containers by the inter-engaging locking elements on the container.
In a particular embodiment of the invention, the bottom of one container is free to move longitudinally relative to the top of a container stacked immediately therebelow, with the recessed portions of the bottom of the upper container translated along tps of the extended side walls of the lower container. This feature, allowing for one degree of freedom of movement in the planr the containers at the top of a stack, is particularly advantageous for use of a semi-mechanized handling system for such contain on a smaller vessel, permitting the coordinated use of manual sliding and mechanical lifting of containers when on deck for charging and discharging their contents. High stacking strength is achieved by exterior vertical corrugations in the side walls of the container, which is further rigidified by a stiffener rod fastened between the side walls. The stiffener rod also provides support for a cover that fits closely between the side walls and curves over the end walls of the container in a frictional fit.